Internal combustion engines (e.g., 4-stroke engines) use valves to control the flow of combustion gases into and out of a combustion chamber defined in part by a piston situated within a cylinder that is coupled and drives an engine's crankshaft. Several different types of valve mechanisms are commonly used and are conventionally known as poppet valves, rotary valves, slide (or sliding) valves, piston valves, and hinged valves.
Although poppet valves are the most common valve used to control the flow of gases into and out of the combustion chamber in internal combustion engines, they suffer from several shortcomings. For example, as conventional poppet (e.g., intake and exhaust) valves typically use spring for closing the valves, when operating engines at high revolutions-per-minute (RPM), poppet valves can float, which can result in damage to the engines, loss of efficiency, and an increase in exhaust emissions. Accordingly, to reduce the likelihood of valve float, a secondary valve spring is often used in combination with a primary valve spring. However, using two springs increases forces on the valve train, which would require a more robust valve train, which can increase cost and add complexity. Further, during operation, a valve spring converts kinetic energy to friction energy, which reduces efficiency of an engine.
Further, conventional poppet valves can be operated using solid or hydraulic lifters. Solid lifters must be adjusted periodically during an engine's lifespan so that proper lash is maintained. Further, if proper valve lash is not maintained, the valves may be damaged (e.g., due to overheating, in the case of too little lash, or mushrooming, in the case of too much lash), and the engine may lose efficiency. Accordingly, many engines use hydraulic lash adjusters, which increases costs and pumping losses, as well as complexity.
Further, as an overhead-type poppet valve protrudes into at least part of the combustion chamber when opened, the location of a poppet valve and/or a corresponding piston must be controlled so that the valve does not contact the piston during operation. Accordingly, either or both the piston and the valve must be shaped, sized, and/or located, so as to insure that proper distance is maintained between the valve and piston at all times. This can increase design costs and result in a less than optimum valve train design and/or construction. For example, the size and the travel of the valve is often limited so as to prevent the valve from striking the piston during operation, which can adversely affect the flow through the valve and reduce the efficiency of the engine.
Accordingly, may attempts have been made to design other types of intake and/or exhaust valves for internal combustion engines. For example, rotary valve engines such as those which are described in, for example, U.S. Pat. No. 5,878,707 entitled ROTARY VALVE INTERNAL COMBUSTION ENGINE, to Ballard, etc., has been disclosed. However, rotary valves typically suffer from poor sealing and lubrication. Accordingly, many attempts have been made to provide better sealing and/or lubrication of the valves in engines of this type (e.g., see, U.S. Pat. No. 2,296,081, entitled “LUBRICATION OF ROTARY VALVES,” to Metcalf, and U.S. Pat. No. 5,967,108 entitled “ROTARY VALVE SYSTEM,” to Kutlucinar). However, to date rotary valves have still not become a commercial success.
With regard to the slide valve engines, these valves are also well known in the art and are described in, for example, U.S. Pat. No. 1,273,002, entitled “SLIDE VALVE MECHANISM,” to Samuels; U.S. Pat. No. 1,537,248 entitled “INTERNAL COMBUSTION ENGINE,” to Maloney; and U.S. Pat. No. 2,409,350 entitled “INTERNAL-COMBUSTION ENGINE,” to Forrest. Typically, these engines uses a plate having an aperture which is aligned with a manifold to flow connect the combustion chamber to the manifold. Similarly to the rotary valve engines, these valves also suffer from lubrication and sealing problems.
With regard to piston-type valves, such as, those which are disclosed in U.S. Pat. No. 1,303,748 entitled “VALVE GEAR FOR INTERNAL COMBUSTION ENGINES,” to Wattel; U.S. Pat. No. 1,332,265, entitled “GASOLINE-MOTOR,” to Lehman, and U.S. Pat. No. 2,202,292 entitled “INTERNAL COMBUSTION ENINGE,” to Hickey, among other deficiencies, these piston-type valves suffer from sealing problems.
Accordingly, there is a need for an internal combustion engine valve apparatus which can reduce or eliminate the problems and disadvantages of the prior art.